Issue

• path_checker=directio fails under heavy I/O load. multipath devices are marked as down when directio times out on both paths.   This is only marked down for less than a minute  but if kjournald is writing to the disk at this time it fail and  mark the file system as read-only and preventing long running jobs from writing to the disk.  The file system needs to be  unmounted ; then mounted again(mount -o remount,rw) does not work or sometimes a reboot is required.
• path_checker=tur works no better.   there are no timeouts but seems to have extreme performance problems.